2023A&A...671A..33S


Query : 2023A&A...671A..33S

2023A&A...671A..33S - Astronomy and Astrophysics, volume 671A, 33 (2023/3-1)

Supersoft luminous X-ray sources in galactic nuclei.

SACCHI A., RISALITI G. and MINIUTTI G.

Abstract (from CDS):

Context. Tidal disruption events (TDEs) are usually discovered at X-ray or optical wavelengths through their transient nature. A characteristic spectral feature of X-ray detected TDEs is a 'supersoft' X-ray emission, not observed in any other extragalactic source, with the exception of a few rapidly variable hyperluminous X-ray sources (HLXs) or supersoft active galactic nuclei (AGN) that are distinguishable by their optical emission.
Aims. The goal of our work is to find extragalactic supersoft sources associated with galactic centres. We expect this category to include overlooked TDEs, supersoft AGN, and nuclear HLXs. Finding such sources would allow for the study of extreme regime accretion on different black hole mass scales.
Methods. We searched for supersoft X-ray sources (SSSs) by cross-correlating optical and X-ray catalogues to select extragalactic near-nuclear sources and we then filtered for very steep spectra (photon index Γ > 3) and high X-ray luminosities (LX > 1041 erg s–1).
Results. With our blind search we retrieved about 60 sources, including 15 previously known supersoft AGN or TDEs, thus demonstrating the efficiency of our selection. Of the remaining sample, 36 sources are optically classified as AGN, although they show steeper-than-usual spectra. The remaining nine previously unknown sources show spectral properties consistent with emission by extremely soft-excess dominated AGN (five sources) or TDEs (four sources). An XMM-Newton follow-up observation of one of these sources confirmed its likely TDE nature.
Conclusions. Our work is the first attempt to discover TDEs by their spectral features rather than their variability, and it has been successful in retrieving known TDEs and in discovering new extreme ultrasoft sources, including four new TDE candidates, one of which is confirmed via follow-up observations.

Abstract Copyright: © The Authors 2023

Journal keyword(s): galaxies: nuclei - X-rays: galaxies - accretion, accretion disks - galaxies: active

Simbad objects: 74

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Number of rows : 74
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 2MASX J00414632-2827423 G 00 41 46.3246168296 -28 27 42.624911628   18.225   16.999   ~ 3 0
2 M 31 AGN 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 12678 1
3 NAME Scl Group GrG 01 00 06 -33 44.2           ~ 509 0
4 SDSS J010006.84-001534.9 AGN 01 00 06.84216 -00 15 34.9344   19.24 18.81     ~ 3 0
5 OGLE16aaa ev 01 07 20.88 -64 16 20.7           ~ 54 0
6 [FWB2009] HLX-1 ULX 01 10 28.30 -46 04 22.3     24.5 23.80   ~ 202 1
7 2dFGRS TGS564Z081 Sy2 01 19 08.6635573080 -34 11 30.527946780   16.226   15.275   ~ 92 0
8 SDSS J011935.29-002033.5 QSO 01 19 35.2904609712 -00 20 33.594914400   20.83 20.57     ~ 21 0
9 M 33 GiG 01 33 50.8965749232 +30 39 36.630403128 6.17 6.27 5.72     ~ 5847 1
10 2MASS J01395577+0619225 Sy1 01 39 55.7697705024 +06 19 22.520805888   16.80 17.00     ~ 180 0
11 SDSS J021704.53-050215.0 AGN 02 17 04.536 -05 02 15.09           ~ 5 0
12 2XLSSd J021728.4-041346 G 02 17 28.20 -04 13 46.1           ~ 2 0
13 2XMM J021938.5-032507 Sy1 02 19 38.7169190832 -03 25 08.251816800   19.0   19.1   ~ 22 0
14 SDSS J022041.63-032700.4 QSO 02 20 41.638 -03 27 00.43           ~ 9 0
15 SDSS J022048.82-040819.5 QSO 02 20 48.822 -04 08 19.58           ~ 8 0
16 3XMM J022131.9-053853 Sy1 02 21 31.9733533920 -05 38 53.908478988           ~ 14 0
17 SDSS J022208.11-042734.7 QSO 02 22 08.1186238872 -04 27 34.712808588   18.78   18.4   ~ 17 0
18 SDSS J022255.89-051351.7 QSO 02 22 55.8911902368 -05 13 51.776817852   18.78   18.65   ~ 17 0
19 LEDA 1061293 AG? 02 49 17.3199268944 -04 12 52.076014416           ~ 40 0
20 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 7084 0
21 2XMM J032159.8-370509 QSO 03 21 59.8908618624 -37 05 09.228729156           ~ 8 1
22 2dFGRS TGS243Z047 AGN 03 31 31.3238495760 -27 28 46.748460684   15.664   14.558   ~ 16 0
23 [VV2006] J033226.5-274036 QSO 03 32 26.4998939520 -27 40 35.910988680 20.34 20.0691   20.091 19.7666 ~ 75 0
24 2XMM J033227.1-280124 QSO 03 32 27.131 -28 01 24.32       19.878   ~ 20 0
25 2XMM J033742.8-252209 AGN 03 37 42.8262877056 -25 22 09.536891124   18.48   17.46   ~ 3 0
26 LEDA 88588 Sy1 07 08 41.4886614696 -49 33 06.308921700   16.02 15.7 12.7   ~ 520 0
27 PS1-13jw ev 08 44 53.560 +42 57 44.84           ~ 4 0
28 [VV2006] J090840.2+394415 QSO 09 08 40.2208982856 +39 44 15.134747712   20.63 20.39     ~ 22 0
29 SDSS J090927.75+542127.9 QSO 09 09 27.7577121672 +54 21 27.930967632           ~ 8 0
30 SDSS J094241.69+464033.1 QSO 09 42 41.6892148704 +46 40 33.179258496           ~ 7 0
31 2MASX J10181928+3722419 Sy2 10 18 19.2421056408 +37 22 42.340498356   16.4       ~ 22 0
32 Z 212-25 Sy1 10 34 38.5982990352 +39 38 28.187042604   17.37 16.90     ~ 365 1
33 [VV2000] J110838.3+255522 QSO 11 08 38.3154334320 +25 55 21.439160148   17.5 18.35 18.2   ~ 20 0
34 RX J1119.7+5951 Sy1 11 19 41.1310526856 +59 51 08.643793176   17.76 17.57     ~ 36 0
35 3XMM J115546.6+232446 Sy1 11 55 46.6541511600 +23 24 46.602230436           ~ 17 0
36 2MASS J12013602+3003052 G 12 01 36.0281668104 +30 03 05.576406012           ~ 42 0
37 [VV2006] J120644.1+495337 QSO 12 06 44.0251856832 +49 53 36.741862680   18.28 18.08     ~ 26 0
38 2XMM J120650.1+442353 Sy1 12 06 50.1147761544 +44 23 53.590124868   19.88 19.58     ~ 23 0
39 SDSS J120947.76+393042.2 QSO 12 09 47.7536449248 +39 30 42.231248928           ~ 6 0
40 SDSS J122517.68+175726.4 QSO 12 25 17.6822851560 +17 57 26.235011664   19.2   19.3   ~ 12 0
41 2XMM J123103.2+110648 AG? 12 31 03.239 +11 06 48.60           ~ 46 0
42 SDSSCGA 1202 CGG 12 34 07.6 +09 05 37           ~ 3 0
43 SDSS J123408.85+090542.4 BiC 12 34 08.8644374712 +09 05 42.408232836           ~ 7 0
44 [VV2006] J124049.1-015524 QSO 12 40 49.1112678096 -01 55 23.428271712     19.47     ~ 14 0
45 LEDA 43234 AG? 12 48 15.2253025968 +17 46 26.475426228   16.5       ~ 265 0
46 SDSS J125749.86+473958.9 QSO 12 57 49.8640176264 +47 39 58.923727740           ~ 7 0
47 LEDA 140041 Sy1 12 58 21.3138751296 +01 31 58.517380452   19.37 19.00     ~ 17 0
48 2MASX J13020015+2746579 AGN 13 02 00.1383745104 +27 46 57.854731080   15.4       ~ 112 0
49 LEDA 88835 Sy1 13 25 19.3805530608 -38 24 52.611680340   16.64 13.80 15.33 14.78 ~ 421 0
50 [VV2006] J133944.5-001452 QSO 13 39 44.5070747544 -00 14 51.517474044   19.33 19.11     ~ 33 0
51 PG 1404+226 Sy1 14 06 21.8900886888 +22 23 46.515550056   16.62 16.42     ~ 235 0
52 SDSS J141130.19+002819.6 G 14 11 30.1914559272 +00 28 19.728854508           ~ 4 0
53 SDSS J141308.12+515210.5 Sy1 14 13 08.1011094336 +51 52 10.428933612           ~ 20 0
54 SDSS J141711.07+522540.8 AGN 14 17 11.0814 +52 25 40.713   22.251 21.182 19.92 19.665 ~ 19 0
55 3XMM J150052.0+015452 BH 15 00 52.01 +01 54 52.7           ~ 21 0
56 SDSS J150052.07+015453.8 G 15 00 52.07088 +01 54 53.8236           ~ 3 0
57 3XMM J152130.7+074916 X 15 21 30.7 +07 49 16           ~ 16 0
58 SDSS J152717.95+164503.2 G 15 27 17.9443751592 +16 45 03.174919344           ~ 4 0
59 SDSS J161212.57+540936.5 QSO 16 12 12.5770502520 +54 09 36.652878252 18.23 18.5   19.1 19.01 ~ 14 0
60 NGC 6264 Sy2 16 57 16.1272966344 +27 50 58.574330124   15.5       ~ 108 1
61 2MASX J17020882+6412210 H2G 17 02 08.8842001104 +64 12 21.134246796     16.66     ~ 14 0
62 3XMM J172037.1+574855 Sy1 17 20 37.1529033192 +57 48 56.188018152   19.49 18.93     ~ 9 0
63 2MASS J18472513-6317252 G 18 47 25.1287042560 -63 17 25.304943912     16.67   15.56 ~ 13 0
64 2MASX J19271951+6533539 Sy1 19 27 19.5393064368 +65 33 54.335877408     15.4     ~ 90 0
65 ASASSN -15oi SN* 20 39 09.096 -30 45 20.71           ~ 129 0
66 [CRS2013] 4 G 22 26 08.660 +17 24 17.15           ~ 3 0
67 ACO 2443 ClG 22 26 14.09 +17 25 13.5           ~ 104 0
68 [VV2006] J231419.8-525901 QSO 23 14 19.8764439072 -52 59 01.069382220           ~ 9 0
69 3XLSS J231800.4-534901 AGN 23 18 00.4194538680 -53 49 01.608841488           ~ 3 0
70 XXL-AAOmega J231814.50-544112.3 AGN 23 18 14.4 -54 41 12           ~ 2 0
71 3XLSS J232605.5-540559 AGN 23 26 05.3 -54 06 00           ~ 3 0
72 [GHC2009] D23H-1 G 23 31 59.5395591768 +00 17 14.595290952   20.67   19.30 18.83 ~ 25 0
73 XXL-AAOmega J234255.95-543001.8 AGN 23 42 55.9 -54 30 02           ~ 2 0
74 2dFGRS TGS431Z029 G 23 57 24.3465087264 -32 42 34.157130408   16.278   15.192   ~ 8 0

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